FemtoLab: Dhiman Das

Dhiman Das

Education / Work History

Ph.D. Scholar, IIT Kanpur (2017)
M.Sc., IIT Guwahati (2008-2010)

Thesis Abstract

Spatiotemporal Approaches Towards Enhancing the Efficiency of Laser Scanning Fluorescence Microscopy in Condensed Phase

This thesis mainly focuses on application of third-order nonlinear optical phenomena including self-defocusing effect of binary liquid mixtures to probe intermolecular interaction and modulation of two photon fluorescence in far-field microscopy. Spatiotemporal control of two photon fluorescence (TPF) as well as resolution benefits obtained with temporally controlled femtosecond pulse in the field of multi-photon fluorescence microscopy are the major highlights of this thesis. It begins with a discussion on the chronological evolution of fluorescence experiments and their applications, continuing all the way to the development of modern super-resolved fluorescence microscopy (Chapter 1). This sets up the motivation of the present work reported in the thesis as well as discusses the existing open problems about control of TPF in microscopy. Chapter 2 describes the instrumentation part in detail for all the experiments being presented in this thesis. Chapter 3 involves a brief discussion on measurement of third-order optical nonlinearity, in particular, on nonlinear absorption and nonlinear refraction and the standard home-built z-scan technique to simultaneously measure nonlinear absorption and nonlinear refraction in solids, liquids and liquid solutions within the “thin sample approximation”. In Chapter 4, it has been shown that such thermo-optic results can have a far-reaching impact on molecular properties and intermolecular interactions in binary liquid mixtures. Chapter 5 aims at focusing on photo-physical processes that occur in a typical fluorophore and their association to one-photon and two photon fluorescence microscopy. In Chapter 6, control of TPF in microscopy is discussed with one color pulse-pair excitation scheme using femtosecond laser pulses. Chapter 7 focuses on the effect of our one color pulse-pair technique to enhance the axial resolution as a function of the relative time delay between the pulse pair in two photon fluorescence microscopy. Chapter 8 is the concluding chapter that summarizes how to probe intermolecular interactions in binary liquid mixtures using HRR femtosecond laser induced self-defocusing nonlinearity under non-resonant condition. Most importantly, we have shown spatiotemporal control of the two-photon fluorescence process and consequent resolution enhancement in both lateral and axial direction in two photon fluorescence microscopy. Based on the current results and discussions presented in this thesis, further possible experiments have been proposed. The work presented in this thesis is the endeavor to bring the concept of dynamical control to a new horizon and to throw a deeper insight on the spatiotemporal control of two photon fluorescence process in far-field microscopy. Further advances in this emerging research field are expected to enrich our understanding in condensed phase molecular dynamics at the single molecular level.

Research Topic / Interest

Contact me to know my current interests.

Publications

These include only those published in our lab.

Direct Observation of Diatoms Pair Formation in Aqueous Solution Under Laser Scanning Fluorescence Microscopy. D. Das and D. Goswami, in 13th International Conference on Fiber Optics and Photonics (OSA, 2016), p. Tu2B.3 [Abstract] [PDF] [BibTeX]
Abstract: We show important applications of our imaging technique in visualizing the morphology as well as division of diatoms in aqueous solution. The technique involves the efficient detection of the auto-fluorescence from chloroplast and shell structure through laser scanning confocal microscopy.
```
 BibTeX: @inproceedings{dasDirectObservationDiatoms2016,
  title = {Direct {{Observation}} of {{Diatoms Pair Formation}} in {{Aqueous Solution Under Laser Scanning Fluorescence Microscopy}}},
  booktitle = {13th {{International Conference}} on {{Fiber Optics}} and {{Photonics}}},
  author = {Das, Dhiman and Goswami, Debabrata},
  date = {2016},
  pages = {Tu2B.3},
  publisher = {{OSA}},
  location = {{Kharagpur}},
  doi = {10/gf5mrq},
  url = {https://my.pcloud.com/publink/show?code=XZrNxr7ZTM0YMQbaakBFrDr1GOUzFXGBIn6V},
  urldate = {2019-08-01},
  eventtitle = {International {{Conference}} on {{Fibre Optics}} and {{Photonics}}},
  isbn = {978-1-943580-22-4}
}
```
Spatiotemporal Control of Degenerate Multiphoton Fluorescence Microscopy with Delay-Tunable Femtosecond Pulse Pairs. D. Das, I. Bhattacharyya, and D. Goswami, Chemical Physics Letters 657, 72–77 (2016) [Abstract] [PDF] [BibTeX]
Abstract: Selective excitation of a particular fluorophore in an ensemble of different fluorophores with overlapping fluorescence spectra is shown to be dependent on the time delay of femtosecond pulse pairs in multiphoton fluorescence microscopy. In particular, the two-photon fluorescence behavior of the Texas Red and DAPI dye pair inside Bovine Pulmonary Artery Endothelial (BPAE) cells depends strongly on the center wavelength of the laser, as well as the delay between two identical laser pulses in one-color femtosecond pulse-pair excitation scheme. Thus, we present a novel design concept using pairs of femtosecond pulses at different central wavelengths and tunable pulse separations for controlling the image contrast between two spatially and spectrally overlapping fluorophores. This femtosecond pulse-pair technique is unique in utilizing the variation of dye dynamics inside biological cells as a contrast mode in microscopy of different fluorophores.
```
 BibTeX: @article{dasSpatiotemporalControlDegenerate2016,
  title = {Spatiotemporal Control of Degenerate Multiphoton Fluorescence Microscopy with Delay-Tunable Femtosecond Pulse Pairs},
  author = {Das, Dhiman and Bhattacharyya, Indrajit and Goswami, Debabrata},
  date = {2016-07-16},
  journaltitle = {Chemical Physics Letters},
  shortjournal = {Chemical Physics Letters},
  volume = {657},
  pages = {72--77},
  issn = {0009-2614},
  doi = {10/f84rwd},
  url = {https://my.pcloud.com/publink/show?code=XZ1Axr7ZxiTGNbfEV1bmLPqho9PtQzSq3qUk},
  urldate = {2019-08-01}
}
```
Resolution Enhancement through Microscopic Spatiotemporal Control. D. Goswami, D. Das, and S. N. Bandyopadhyay, Faraday Discussions 177(0), 203–212 (2015) [Abstract] [PDF] [BibTeX]
Abstract: Operating at biologically benign conditions, multi-photon fluorescence imaging microscopy has benefitted immensely from recent developments in microscopic resolution enhancement. Fluorescence microscopy continues to be the best choice for experiments on live specimens, however, multi-photon fluorescence imaging often suffers from overlapping fluorescence of typical dyes used in microscopy, limiting its scope. This limitation has been the focus of our research where we show that by making simple modifications to the laser pulse structure, it is possible to resolve these overlapping fluorescence complications. Specifically, by using pairs of femtosecond pulses with variable delay in place of single pulse excitation, we show controlled fluorescence excitation or suppression of one of the fluorophores over the other through wave-packet interferometry. Such an effect prevails even after the fluorophore coherence timescale, which effectively results in a higher spatial resolution. Here we extend the effect of our pulse-pair technique to microscopic axial resolution experiments and show that such pairs of pulses can also ‘enhance’ axial resolution.
```
 BibTeX: @article{goswamiResolutionEnhancementMicroscopic2015,
  title = {Resolution Enhancement through Microscopic Spatiotemporal Control},
  author = {Goswami, Debabrata and Das, Dhiman and Bandyopadhyay, Soumendra Nath},
  date = {2015-04-14},
  journaltitle = {Faraday Discussions},
  shortjournal = {Faraday Discuss.},
  volume = {177},
  number = {0},
  pages = {203--212},
  issn = {1364-5498},
  doi = {10/gf5msv},
  url = {https://my.pcloud.com/publink/show?code=XZzvxr7Z0vbvki6gLSQhR76QzRco87Moa8Fy},
  urldate = {2019-08-01}
}
```
Probing Intermolecular Interactions in Binary Liquid Mixtures Using Femtosecond Laser-Induced Self-Defocusing. S. K. Maurya, D. Das, and D. Goswami, Applied Spectroscopy 70(10), 1655–1661 (2016) [Abstract] [PDF] [BibTeX]
Abstract: Photothermal behavior of binary liquid mixtures has been studied using a high repetition rate (HRR) Z-scan technique with femtosecond laser pulses. Changes in the peak–valley difference in transmittance (ΔTP–V) for closed aperture Z-scan experiments are indicative of thermal effects induced by HRR femtosecond laser pulses. We show such indicative results can have a far-reaching impact on molecular properties and intermolecular interactions in binary liquid mixtures. Spectroscopic parameters derived from this experimental technique show that the combined effect of physical and molecular properties of the constituent binary liquids can be related to the components of the binary liquid.
```
 BibTeX: @article{mauryaProbingIntermolecularInteractions2016,
  title = {Probing {{Intermolecular Interactions}} in {{Binary Liquid Mixtures Using Femtosecond Laser-Induced Self-Defocusing}}},
  author = {Maurya, Sandeep Kumar and Das, Dhiman and Goswami, Debabrata},
  date = {2016-10-01},
  journaltitle = {Applied Spectroscopy},
  shortjournal = {Appl Spectrosc},
  volume = {70},
  number = {10},
  pages = {1655--1661},
  issn = {0003-7028},
  doi = {10/gf5mrx},
  url = {https://doi.org/10.1177/0003702816643547},
  urldate = {2019-08-01}
}
```
Direct Observation of Diatoms Pair Formation in Aqueous Solution Under Laser Scanning Fluorescence Microscopy. D. Das and D. Goswami, in 13th International Conference on Fiber Optics and Photonics (OSA, 2016), p. Tu2B.3 [Abstract] [PDF] [BibTeX]
Abstract: We show important applications of our imaging technique in visualizing the morphology as well as division of diatoms in aqueous solution. The technique involves the efficient detection of the auto-fluorescence from chloroplast and shell structure through laser scanning confocal microscopy.
```
 BibTeX: @inproceedings{dasDirectObservationDiatoms2017,
  langid = {english},
  location = {{Kharagpur}},
  title = {Direct {{Observation}} of {{Diatoms Pair Formation}} in {{Aqueous Solution Under Laser Scanning Fluorescence Microscopy}}},
  isbn = {978-1-943580-22-4},
  url = {https://my.pcloud.com/publink/show?code=XZrNxr7ZTM0YMQbaakBFrDr1GOUzFXGBIn6V},
  doi = {10.1364/PHOTONICS.2016.Tu2B.3},
  eventtitle = {International {{Conference}} on {{Fibre Optics}} and {{Photonics}}},
  booktitle = {13th {{International Conference}} on {{Fiber Optics}} and {{Photonics}}},
  publisher = {{OSA}},
  urldate = {2019-08-01},
  date = {2016},
  pages = {Tu2B.3},
  author = {Das, Dhiman and Goswami, Debabrata}
}
```
Probing Intermolecular Interactions in Binary Liquid Mixtures Using Femtosecond Laser-Induced Self-Defocusing. S. K. Maurya, D. Das, and D. Goswami, Appl Spectrosc 70(10), 1655–1661 (2016) [Abstract] [PDF] [BibTeX]
Abstract: Photothermal behavior of binary liquid mixtures has been studied using a high repetition rate (HRR) Z-scan technique with femtosecond laser pulses. Changes in the peak–valley difference in transmittance (ΔTP–V) for closed aperture Z-scan experiments are indicative of thermal effects induced by HRR femtosecond laser pulses. We show such indicative results can have a far-reaching impact on molecular properties and intermolecular interactions in binary liquid mixtures. Spectroscopic parameters derived from this experimental technique show that the combined effect of physical and molecular properties of the constituent binary liquids can be related to the components of the binary liquid.
```
 BibTeX: @article{mauryaProbingIntermolecularInteractions2017,
  langid = {english},
  title = {Probing {{Intermolecular Interactions}} in {{Binary Liquid Mixtures Using Femtosecond Laser}}-{{Induced Self}}-{{Defocusing}}},
  volume = {70},
  issn = {0003-7028},
  url = {https://doi.org/10.1177/0003702816643547},
  doi = {10/gf5mrx},
  number = {10},
  journaltitle = {Appl Spectrosc},
  urldate = {2019-08-01},
  date = {2016-10-01},
  pages = {1655-1661},
  author = {Maurya, Sandeep Kumar and Das, Dhiman and Goswami, Debabrata}
}
```
Spatiotemporal Control of Degenerate Multiphoton Fluorescence Microscopy with Delay-Tunable Femtosecond Pulse Pairs. D. Das, I. Bhattacharyya, and D. Goswami, Chemical Physics Letters 657, 72–77 (2016) [Abstract] [PDF] [BibTeX]
Abstract: Selective excitation of a particular fluorophore in an ensemble of different fluorophores with overlapping fluorescence spectra is shown to be dependent on the time delay of femtosecond pulse pairs in multiphoton fluorescence microscopy. In particular, the two-photon fluorescence behavior of the Texas Red and DAPI dye pair inside Bovine Pulmonary Artery Endothelial (BPAE) cells depends strongly on the center wavelength of the laser, as well as the delay between two identical laser pulses in one-color femtosecond pulse-pair excitation scheme. Thus, we present a novel design concept using pairs of femtosecond pulses at different central wavelengths and tunable pulse separations for controlling the image contrast between two spatially and spectrally overlapping fluorophores. This femtosecond pulse-pair technique is unique in utilizing the variation of dye dynamics inside biological cells as a contrast mode in microscopy of different fluorophores.
```
 BibTeX: @article{dasSpatiotemporalControlDegenerate2017,
  title = {Spatiotemporal Control of Degenerate Multiphoton Fluorescence Microscopy with Delay-Tunable Femtosecond Pulse Pairs},
  volume = {657},
  issn = {0009-2614},
  url = {https://my.pcloud.com/publink/show?code=XZ1Axr7ZxiTGNbfEV1bmLPqho9PtQzSq3qUk},
  doi = {10/f84rwd},
  journaltitle = {Chemical Physics Letters},
  urldate = {2019-08-01},
  date = {2016-07-16},
  pages = {72-77},
  author = {Das, Dhiman and Bhattacharyya, Indrajit and Goswami, Debabrata}
}
```
Resolution Enhancement through Microscopic Spatiotemporal Control. D. Goswami, D. Das, and S. N. Bandyopadhyay, Faraday Discuss. 177(0), 203–212 (2015) [Abstract] [PDF] [BibTeX]
Abstract: Operating at biologically benign conditions, multi-photon fluorescence imaging microscopy has benefitted immensely from recent developments in microscopic resolution enhancement. Fluorescence microscopy continues to be the best choice for experiments on live specimens, however, multi-photon fluorescence imaging often suffers from overlapping fluorescence of typical dyes used in microscopy, limiting its scope. This limitation has been the focus of our research where we show that by making simple modifications to the laser pulse structure, it is possible to resolve these overlapping fluorescence complications. Specifically, by using pairs of femtosecond pulses with variable delay in place of single pulse excitation, we show controlled fluorescence excitation or suppression of one of the fluorophores over the other through wave-packet interferometry. Such an effect prevails even after the fluorophore coherence timescale, which effectively results in a higher spatial resolution. Here we extend the effect of our pulse-pair technique to microscopic axial resolution experiments and show that such pairs of pulses can also ‘enhance’ axial resolution.
```
 BibTeX: @article{goswamiResolutionEnhancementMicroscopic2016,
  langid = {english},
  title = {Resolution Enhancement through Microscopic Spatiotemporal Control},
  volume = {177},
  issn = {1364-5498},
  url = {https://my.pcloud.com/publink/show?code=XZzvxr7Z0vbvki6gLSQhR76QzRco87Moa8Fy},
  doi = {10/gf5msv},
  number = {0},
  journaltitle = {Faraday Discuss.},
  urldate = {2019-08-01},
  date = {2015-04-14},
  pages = {203-212},
  author = {Goswami, Debabrata and Das, Dhiman and Bandyopadhyay, Soumendra Nath}
}
```

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Dhiman Das

Education / Work History

Thesis Abstract

Spatiotemporal Approaches Towards Enhancing the Efficiency of Laser Scanning Fluorescence Microscopy in Condensed Phase

Research Topic / Interest

Publications